Thin film structure and manufacturing method therefor

ABSTRACT

The present invention provides a thin film structure configured such that: thin films  8   a  and  8   b  and an electrode pad  7  are provided on a substrate  5;  and a nonconductive shielding film  11  is formed on the sides of the thin films  8   a  facing the electrode pad  7  such that the top surface of the shielding film  11  is higher than the top surface of the electrode pad  7.  That is, the shielding film  11  covers the top surfaces and sides of the thin films  8   a  between adjacent electrode pads. This arrangement allows one to reduce the parasitic capacitance between adjacent electrode pads and prevent a change in the characteristics, as well as canceling the fringe effect.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin film structure and amanufacturing method therefor, and more particularly to a thin filmstructure for use in a semiconductor acceleration sensor and amanufacturing method therefor.

2. Background Art

Semiconductor acceleration sensors have been used in control systems forautomobile suspensions, air bags, etc. For example, Japanese PatentLaid-Open No. Hei 9-211022 discloses a semiconductor acceleration sensorin which thin film structures such as stationary and movable electrodesare formed on a substrate.

In such an acceleration sensor, the main body including the thin filmstructures is enclosed in a hermetic package for protection. Thestationary and movable electrodes are connected to the electrode pads,which are exposed outside the device.

SUMMARY OF THE INVENTION

The above conventional acceleration sensor is disadvantageous in that ifa gap is formed between the package and the electrode pads as a resultof detachment of the package from the pads due to external stress, etc.,then moisture, etc. may enter the gap, resulting in formation ofparasitic capacitance between the electrode pads. This causes the thinfilm structures to suffer electrical leakage and a change in theircharacteristics. Furthermore, the fringe effect around the electrodesadversely affects the device characteristics.

The present invention has been devised in view of the above problems. Itis, therefore, an object of the present invention to provide a thin filmstructure for use in a semiconductor acceleration sensor housed in aprotective package and a manufacturing method therefor, wherein the thinfilm structure has an electrode structure capable of reducing theparasitic capacitance between the electrode pads to prevent a change inthe characteristics, as well as canceling the fringe effect.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view showing a thin film structure of thefirst embodiment;

FIG. 2 is a cross-sectional view showing a manufacturing method of athin film structure of the first embodiment;

FIG. 3 is a cross-sectional view showing a manufacturing method of athin film structure of the first embodiment;

FIG. 4 is a cross-sectional view showing a manufacturing method of athin film structure of the first embodiment;

FIG. 5 is a cross-sectional view showing a manufacturing method of athin film structure of the first embodiment;

FIG. 6 is a cross-sectional view showing a manufacturing method of athin film structure of the first embodiment;

FIG. 7 is a cross-sectional view showing a manufacturing method of athin film structure of the first embodiment;

FIG. 8 is a cross-sectional view showing a thin film structure of thesecond embodiment;

FIG. 9 is a cross-sectional view showing a manufacturing method of athin film structure of the second embodiment;

FIG. 10 is a cross-sectional view showing a manufacturing method of athin film structure of the second embodiment;

FIG. 11 is a cross-sectional view showing a thin film structure of thethird embodiment;

FIG. 12 is a cross-sectional view showing a thin film structure of thefourth embodiment;

FIG. 13 is a cross-sectional view showing a thin film structure of thefifth embodiment;

FIG. 14 is a cross-sectional view showing a manufacturing method of athin film structure of the fifth embodiment;

FIG. 15 is a cross-sectional view showing a manufacturing method of athin film structure of the fifth embodiment;

FIG. 16 is a cross-sectional view showing a manufacturing method of athin film structure of the fifth embodiment;

FIG. 17 is a cross-sectional view showing a manufacturing method of athin film structure of the fifth embodiment;

FIG. 18 is a cross-sectional view showing a thin film structure of thesixth embodiment;and

FIG. 19 is a cross-sectional view showing a thin film structure of theseventh embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

Now, embodiments of the present invention will be described withreference to the drawings. Like reference numerals denote likecomponents throughout the drawings, and redundant descriptions will beomitted.

First Embodiment

FIG. 1 shows a cross-sectional view of a thin film structure accordingto a first embodiment of the present invention. This thin film structureis used in a semiconductor acceleration sensor, etc. A first insulatingfilm 2 is provided on a silicon substrate 1. A conductive wire 3 isburied in the surface of the first insulating film 2. There is nodifference in height between the top surface of the first insulatingfilm 2 and the top surface of the wire 3; that is, the overall topsurface is substantially flat. A second insulating film 4 is provided onthe first insulating film 2 and the wire 3. The second insulating film 4is formed of a silicon nitride film. (The term “substrate 5” ishereinafter used to refer to the film stack made up of the siliconsubstrate 1, the first insulating film 2, the wire 3, and the secondinsulating film 4.) Holes 6 a and 6 b are formed so as to penetrate thesecond insulating film 4 on the surface of the wire 3. A conductiveelectrode pad 7 is formed on the substrate 5 such that it is locatedover the hole 6 a. The electrode pad 7 is connected to the wire 3through the hole 6 a.

The portions denoted by reference numeral A in the figure adjacent toboth sides of the electrode pad 7 are hereinafter referred to as“proximal portions A”. The portion denoted by reference numeral Boutside the proximal portions A is hereinafter referred to as“nonproximal portion B”. Each proximal portion A includes a thin film 8a. The thin film 8 a is electrically conductive and is made up of asupport portion 8 c and a floating portion 8 d. The support portion 8 cis formed on the second insulating film 4. The floating portion 8 d issupported on the support portion 8 c and thereby spaced a predetermineddistance apart from the second insulating film 4. The top surface of thefloating portion 8 d, that is, the top surface of the thin film 8 a, ishigher than the top surface of the electrode pad 7.

The nonproximal portion B includes a thin film 8 b. The thin film 8 b iselectrically conductive and is made up of a support portion 8 e and afloating portion 8 f. The support portion 8 e is formed over the hole 6b and connected to the wire 3. The floating portion 8 f is supported onthe support portion 8 e and thereby spaced a predetermined distanceapart from the second insulating film 4. Thus, the thin films 8 a and 8b are electrically conductive and have a structure that allows them tobe displaced in response to an applied acceleration.

A third insulating film 10 is formed on the top surface of each floatingportion 8 d and on the side of each floating portion 8 d closest to theelectrode pad 7. This film is made up of, for example, a silicon nitridefilm. A shielding film 11 is laminated over the third insulating film10. This film is, for example, an undoped polysilicon film (anonconductive film). Holes 12 are formed so as to penetrate the thirdinsulating film 10 on the top surfaces of the respective floatingportions 8 d. The shielding film 11 is connected to the thin films 8 athrough the holes 12. Thus, the shielding film 11 covers the top surfaceof each thin film 8 a and the side of each thin film 8 a facing theelectrode pad 7.

The above third insulating film 10 is a diffusion blocking film forpreventing diffusion of conductive substances (i.e., impuritiescontained in the thin films 8 a) from the thin films 8 a into theshielding film 11. Further, the holes 12 are used to prevent theshielding film 11 from becoming detached from the thin films 8 a duringthe process of manufacturing the thin film structure.

Though not shown in FIG. 1, there are actually a plurality of electrodepads 7 formed on the substrate 5. Specifically, two electrode pads 7 aredisposed on respective sides of each thin film 8 a. That is, on thesubstrate 5, each thin film 8 a is sandwiched between a pair ofelectrode pads 7. Sides of each electrode pad 7 faces the shielding film11. The top surface of the shielding film 11 is higher than the topsurfaces of the electrode pads 7.

This configuration allows the parasitic capacitance between adjacentelectrode pads to be reduced even when moisture, etc. enters between thepackage and the electrode pads. Therefore, it is possible to cancel thefringe effect between adjacent electrode pads and thereby prevent achange in the characteristics.

There will now be described a method for manufacturing the thin filmstructure shown in FIG. 1.

First of all, a first insulating film made up of a silicon oxide film isformed on a silicon substrate. Then, the surface of the first insulatingfilm is selectively etched to form a groove. After that, a metal filmmade of tungsten, etc. is formed on the entire surface so as to fill thegroove. Then, unwanted portions of the metal film are removed, leavingonly the portion of the metal film in the groove. The resultantstructure is such that the first insulating film 2 is formed on thesilicon substrate 1, and the conductive wire 3 is formed on the surfaceof the first insulating film 2, as shown in FIG. 2. There issubstantially no difference in height between the top surface of thefirst insulating film 2 and the top surface of the wire 3; that is, theoverall top surface is flat.

Then, a silicon nitride film is formed on the exposed surfaces of thefirst insulating film 2 and the wire 3 shown in FIG. 2. As a result, thesecond insulating film 4 is formed on the first insulating film 2 andthe wire 3, as shown in FIG. 3. Thus, the substrate 5 is formed, inwhich the first insulating film 2, the wire 3, and the second insulatingfilm 4 are laminated to one another over the silicon substrate 1.

Then, the second insulating film 4 on the wire 3 is selectively etchedto form the holes 6 a and 6 b on the wire 3, as shown in FIG. 3.

Then, a silicon oxide film is formed on the entire surface of the secondinsulating film 4 shown in FIG. 3. After that, the silicon oxide film isselectively etched to form a sacrificial film 13 on the secondinsulating film 4, as shown in FIG. 4. The sacrificial film 13 hasgroove patterns 14 a, 14 b and 14 c formed therein. It should be notedthat the second insulating film 4 and the hole 6 a are exposed at thebottom surface of the groove 14 a. Further, the hole 6 b is exposed atthe bottom surface of the groove pattern 14 b, and the second insulatingfilm 4 is also exposed at the bottom surface of the groove pattern 14 c.

Then, a silicon film containing impurities is formed on the entiresurface so as to fill the groove patterns 14 a, 14 b, and 14 c shown inFIG. 4. After that, the silicon film is selectively etched to form thesupport portions 8 c within their respective groove patterns 14 c andfurther form the floating portions 8 d on their respective supportportions 8 c, as shown in FIG. 5. That is, the above step forms theconductive thin films 8 a each made up of a support portion 8 c and afloating portion 8 d. Furthermore, the support portion 8 e is formedwithin the groove pattern 14 b, and the floating portion 8 f is formedon the support portion 8 e. That is, the above step also forms theconductive thin film 8 b made up of the support portion 8 e and thefloating portion 8 f.

Then, a third insulating film made up of a silicon nitride film isformed on the exposed surfaces of the sacrificial film 13 and the thinfilms 8 a and 8 b shown in FIG. 5. Then, the third insulating film isselectively etched to form the third insulating film 10 that covers thetop surfaces of the floating portions 8 d, the sides of the floatingportions 8 d closest to the groove pattern 14 a, and the portions of thesacrificial film 13 constituting the sidewalls of the groove pattern 14a. Further, the holes 12 are formed so as to penetrate the thirdinsulating film 10 on the respective floating portions 8 d. It should benoted that the second insulating film 4 and the hole 6 a are exposed atthe bottom surface of the groove pattern 14 a.

Then, a shielding film made up of a polysilicon film (containing noimpurities) is formed on the exposed surfaces of the sacrificial film 13and the third insulating film 10 shown in FIG. 6. After that, theshielding film is selectively etched to form the shielding film 11covering the third insulating film 10, as shown in FIG. 7. It should benoted that the above step forms the shielding film 11 such that it isconnected to the thin films 8 a through the holes 12. Thus, theshielding film 11 is formed so as to cover the top and side surfaces ofthe thin films 8 a.

Then, the entire sacrificial film 13 shown in FIG. 7 is removed usinghydrofluoric acid, etc. As described above, the shielding film 11 hasbeen formed so as to be connected to the thin films 8 a through theholes 12. Since the shielding film 11 is a polysilicon film and henceinsoluble in hydrofluoric acid, it is not detached from the secondinsulating film 4. Further, since the shielding film 11 is connected tothe thin films 8 a through the holes 12, lift-off of the thin films 8 ais prevented. Still further, since the third insulating film 10 is asilicon nitride film and hence insoluble in hydrofluoric acid, lift-offof the third insulating film 10 from the second insulating film 4 isprevented.

Then, a metal film made of aluminum is formed on the entire surface soas to fill the groove pattern 14 a shown in FIG. 7. After that, themetal film is selectively etched to form the electrode pad 7 over thehole 6 a, as shown in FIG. 1. It should be noted that the top surface ofthe electrode pad 7 is lower than the top surface of the shielding film11.

The above-described manufacturing method allows one to form a thin filmstructure in which the parasitic capacitance between adjacent electrodepads is reduced.

A variation of the above manufacturing method will be described below.

In the above manufacturing method, the step of forming the electrode pad7 (see FIG. 1) is performed after the step of forming the shielding film11 (see FIG. 7). However, the electrode pad 7 may be formed beforeforming the shielding film 11.

Specifically, this method begins by performing the above sequence ofsteps from the step of forming the first insulating film 2 (see FIG. 2)to the step of forming the third insulating film 10 (see FIG. 6). Then,though not shown, on the substrate 5 a pair of electrode pads are formedon respective sides of each thin film 8 a. After that, the thirdinsulating film and the shielding film are formed so as to cover thethin films 8 a. At that time, holes are also formed. The remaining stepsare similar to those of the above original manufacturing method.

This variation also allows one to form a thin film structure in whichthe parasitic capacitance between adjacent electrode pads is reduced.

Second Embodiment

FIG. 8 shows a cross-sectional view of a thin film structure accordingto a second embodiment of the present invention. It should be noted thatthe following description focuses on the differences of the presentembodiment as compared to the first embodiment. In the thin filmstructure of the present embodiment, the shielding film 11 covers thesides and the top edge portions of the electrode pad 7 in addition tothe surfaces of the third insulating film 10. Except for this feature,the thin film structure of the present embodiment is configured in thesame manner as the thin film structure of the first embodiment, andtherefore no further description will be provided.

Thus, according to the present embodiment, the shielding film 11 isformed so as to cover the sides and the top edge portions of theelectrode pad 7. Therefore, the present embodiment can reduce theparasitic capacitance between adjacent electrode pads even further thanthe first embodiment. This allows one to more effectively cancel thefringe effect between adjacent electrode pads, thereby preventing achange in the characteristics.

There will now be described a method for manufacturing the thin filmstructure of the present embodiment.

This method begins by performing the above sequence of steps from thestep of forming the first insulating film 2 on the silicon substrate 1(see FIG. 2) to the step of forming the third insulating film 10 (seeFIG. 6), as in the first embodiment. Then, the electrode pad 7 is formedwithin the groove 14 a shown in FIG. 6 such that it is disposed over thehole 6 a, producing the structure shown in FIG. 9.

Then, a shielding film is formed so as to cover the third insulatingfilm 10, the groove pattern 14 a, and the sides and the top edgeportions of the electrode pad 7 shown in FIG. 9, producing the structureshown in FIG. 10. After that, the entire sacrificial film 13 shown inFIG. 10 is removed, producing the structure shown in FIG. 8.

Thus, in the above manufacturing method of the present embodiment, theshielding film 11 is formed so as to cover the sides and the top edgeportions of the electrode pad 7. Except for this feature, this method issimilar to the above variation of the manufacturing method of the firstembodiment.

The manufacturing method of the present embodiment can form a thin filmstructure in which the parasitic capacitance between adjacent electrodepads is further reduced, as compared to the first embodiment.

Third Embodiment

FIG. 11 shows a cross-sectional view of a thin film structure accordingto a third embodiment of the present invention. It should be noted thatthe following description focuses on the differences of the presentembodiment as compared to the first embodiment.

In the thin film structure of the present embodiment, the edge of thefloating portion 8 d of each proximal portion A is extended toward theelectrode pad 7 side such that the side of the floating portion 8 dfacing the electrode pad 7 is as close to the electrode pad 7 aspossible. In other words, each thin film 8 a and the electrode pad 7 areformed such that they are spaced apart by the smallest possible spacingdetermined by the patterning accuracy.

Specifically, the lithography and etching at the steps of forming thethin films 8 a and forming the electrode pad 7 are performed such thatthe thin films 8 a and the electrode pad 7 are formed as close to eachother as possible as long as there is no possibility that they come intocontact with each other.

At that time, the portions of the shielding film 11 facing the sides ofthe electrode pad 7 are formed such that their top surfaces are higherthan the top surface of the electrode pad 7. Except for these features,the thin film structure of the present embodiment is configured in thesame manner as the thin film structure of the first embodiment, andtherefore no further description will be provided.

Thus, the present embodiment provides a structure in which the portionsof the shielding film 11 close to the electrode pad 7 has a largeheight, as compared to the first embodiment. Therefore, the presentembodiment can reduce the parasitic capacitance between adjacentelectrode pads even further than the first embodiment. This allows oneto more effectively cancel the fringe effect between adjacent electrodepads and prevent a change in the characteristics.

Fourth Embodiment

FIG. 12 shows a cross-sectional view of a thin film structure accordingto a fourth embodiment of the present invention. It should be noted thatthe following description focuses on the differences of the presentembodiment as compared to the third embodiment.

In the thin film structure of the present embodiment, the shielding film11 covers the sides and the top edge portions of the electrode pad 7 inaddition to the exposed surfaces of the third thin insulating film 10.Except for this feature, the thin film structure of the presentembodiment is configured in the same manner as the thin film structureof the third embodiment, and therefore no further description will beprovided.

The above thin film structure of the present embodiment can reduce theparasitic capacitance between adjacent electrode pads even further thanthe thin film structure of the third embodiment shown in FIG. 11. Thisallows one to more effectively cancel the fringe effect between adjacentelectrode pads and prevent a change in the characteristics.

Fifth Embodiment

FIG. 13 shows a cross-sectional view of a thin film structure accordingto a fifth embodiment of the present invention. It should be noted thatthe following description focuses on the differences of the presentembodiment as compared to the first to fourth embodiments.

In the thin film structure of the present embodiment, the electrode pad7 is provided within a groove 15 formed in the surface of the firstinsulating film 2. The wire 3 is formed so as to extend along a side andthe bottom surface of the groove 15. The top surface of the electrodepad 7 is level with or lower than the top surface of the substrate 5.Though not shown, actually, two grooves 15 are provided on respectivesides of each thin films 8 a. Each groove 15 is formed in the surface ofthe substrate 5 and has an electrode pad formed therein.

The second insulating film 4 is formed so as to cover the sides and thebottom surface of the groove 15 as well as the sides and the top edgeportions of the electrode pad 7. The second insulating film 4 is asilicon nitride film. It should be noted that the thin film structure ofthe present embodiment does not include the third insulating film 10,the shielding film 11, and the hole 12 shown in FIG. 1 described inconnection with the first embodiment. Except for these features, thethin film structure of the present embodiment is configured in the samemanner as the thin film structure of the first embodiment, and thereforeno further description will be provided.

The thin film structure of the present embodiment allows the thin films8 a to be formed such that their height is greater than the height ofthe electrode pad 7. Further according to the present embodiment, thesides and the top edge portions of the electrode pad 7 are covered withthe second insulating film 4. This configuration produces the sameeffect as the configuration of the second embodiment in which the sidesand the top edge portions of the electrode pad 7 are covered with theshielding film (see FIG. 8). Therefore, the present embodiment cancancel the fringe effect between adjacent electrode pads and therebyprevent a change in the characteristics more effectively than the firstembodiment.

There will now be described a method for manufacturing the thin filmstructure of the present embodiment.

First of all, a first insulating film is formed on a silicon substrateand then its surface is selectively etched to form a groove. Then, awire is formed so as to extend along the surface of the first insulatingfilm and a side and the bottom surface of the groove. FIG. 14 shows theresultant structure in which: the groove 15 is formed in the surface ofthe silicon substrate 1; and the wire 3 is formed so as to extend alongthe surface of the first insulating film 2 and a side and the bottomsurface of the groove 15. Though not shown in FIG. 14, there areactually a plurality of grooves 15 formed in the surface of thesubstrate.

Then, an electrode pad is formed within the groove 15 shown in FIG. 14.As a result, the electrode pad 7 is formed on the bottom surface of thegroove 15, as shown in FIG. 15. The top surface of the electrode pad 7is level with or lower than the top surface of the substrate 5(see FIG.13).

Then, a silicon nitride film is formed on the exposed surfaces of thefirst insulating film 2, the wire 3, the groove 15, and the electrodepad 7 shown in FIG. 15. After that, the silicon nitride film isselectively etched to form the second insulating film 4 covering thefirst insulating film 2, the wire 3, the groove 15, and the electrodepad 7, as shown in FIG. 16. At that time, the hole 6 b is formed so asto penetrate the second insulating film 4 on the wire 3 outside thegroove 15.

Then, a silicon oxide film is formed on the entire surface of the secondinsulating film 4 shown in FIG. 16. After that, the silicon oxide filmis selectively etched to form the groove pattern 14 a, as shown in FIG.17. Also at this step, the groove pattern 14 b is formed over the hole 6b outside the groove 15, and the groove pattern 14 c is formed on thesecond insulating film 4 outside the groove 15.

Then, a silicon film containing impurities is formed on the entiresurface so as to fill the groove patterns 14 a, 14 b, and 14 c shown inFIG. 17. After that, the silicon film is selectively etched. Then, theportion of the second insulating film 4 on the top surface of theelectrode pad 7 is selectively removed, leaving the second insulatingfilm 4 on the sides and the top edge portions of the electrode pad 7.Then, the entire sacrificial film 13 is removed, producing the structureshown in FIG. 13. Though not shown in FIG. 13, on the substrate 5 eachthin film 8 a is sandwiched between adjacent grooves 15.

Thus, the above manufacturing method covers the sides 15 and the topedge portions of the electrode pad 7 with the second insulating film 4,thereby eliminating the steps of forming the third insulating film 10,the shielding film 11, and the hole 12 described in connection with thefirst embodiment. Therefore, the present embodiment requires fewermanufacturing steps than the first embodiment even though it can achievethe same effect as the first embodiment.

Sixth Embodiment

FIG. 18 shows a cross-sectional view of a thin film structure accordingto a sixth embodiment of the present invention. The followingdescription focuses on the differences of the present embodiment ascompared to the first embodiment.

It should be noted that this figure does not show the thin film portionsdescribed in connection with the first to fifth embodiments. Referringto the figure, a plurality of electrode pads 7 are formed on thesubstrate 5, and shield patterns 16 are formed between adjacentelectrode pads 7. The shield patterns 16 have a larger thickness thanthe electrode pads 7. That is, the top surfaces of the shield patterns16 are higher than the top surfaces of the electrode pads 7. Each shieldpattern is made up of a nonconductive film such as an insulating film (asilicon oxide film, etc.) or an undoped silicon film. Except for thesefeatures, the thin film structure of the present embodiment isconfigured in the same manner as the thin film structure of the firstembodiment, and therefore no further description will be provided.

Thus, the above thin film structure of the present embodiment allows oneto reduce the parasitic capacitance between adjacent electrode pads byincreasing the film thickness of the shield patterns 16. Therefore, thepresent embodiment can cancel the fringe effect between adjacentelectrode pads more easily and hence prevent a change in thecharacteristics more effectively than the first embodiment.

Seventh Embodiment

FIG. 19 shows a plan view of a thin film structure according to aseventh embodiment of the present invention.

The present embodiment provides an arrangement in which adjacentelectrode pads are spaced apart by the greatest possible spacing. Thisarrangement can be applied to any of the thin film structures of thefirst to sixth embodiments. For example, when three electrode pads 7 areto be arranged along an edge of the substrate 5, two of the electrodes 7are disposed on opposing sides of the substrate 5 and the remaining oneis disposed halfway between them. In this configuration, the distance Dbetween adjacent electrode pads is preferably 200 μm more. This allowsthe parasitic capacitance between adjacent electrode pads to be reduced.

The present embodiment allows the first to sixth embodiments to furtherreduce the parasitic capacitance between adjacent electrode pads.Therefore, it is possible to more effectively cancel the fringe effectbetween adjacent electrode pads and prevent a change in thecharacteristics.

1. A thin film structure comprising: a conductive thin film provided ona substrate and adapted to be displaced in response to an appliedacceleration; a pair of electrode pads formed on said substrate suchthat they are disposed on respective sides of said thin film; and anonconductive film covering a top surface of said thin film and the sideof said thin film facing said electrode pads, wherein a top surface ofsaid nonconductive film is higher than top surfaces of said electrodepads.
 2. The thin film structure as claimed in claim 1, wherein saidnonconductive film covers sides and top edge portions of said electrodepads.
 3. The thin film structure as claimed in claim 1, wherein saidthin film and each electrode pad are spaced apart by the smallestpossible spacing determined by the patterning accuracy.
 4. The thin filmstructure as claimed in claim 2, wherein said thin film and eachelectrode pad are spaced apart by the smallest possible spacingdetermined by the patterning accuracy.
 5. A thin film structurecomprising: a conductive thin film provided on a substrate and adaptedto be displaced in response to an applied acceleration; a pair ofelectrode pads provided within their respective grooves formed in asurface of said substrate, wherein said grooves are located onrespective sides of said thin film and wherein top surfaces of saidelectrode pads are level with or lower than a top surface of saidsubstrate; and a nonconductive film covering sides and top edge portionsof said electrode pads.
 6. The thin film structure as claimed in claim1, further comprising: a nonconductive film pattern provided betweensaid pair of electrode pads, wherein a top surface of said nonconductivefilm pattern is higher than said top surfaces of said electrode pads. 7.The thin film structure as claimed in claim 5, further comprising: anonconductive film pattern provided between said pair of electrode pads,wherein a top surface of said nonconductive film pattern is higher thansaid top surfaces of said electrode pads.
 8. The thin film structure asclaimed in claim 1, wherein the distance between said pair of electrodepads is 200 μm or more.
 9. The thin film structure as claimed in claim5, wherein the distance between said pair of electrode pads is 200 μm ormore.
 10. A method for manufacturing a thin film structure, comprisingthe steps of: forming a pair of grooves in a surface of a substrate;forming an electrode pad within each groove, wherein a top surface ofsaid electrode pad is level with or lower than a top surface of saidsubstrate; forming a nonconductive film so as to cover sides and topedge portions of each electrode pad; and forming a conductive thin filmon said substrate such that it is disposed between said pair of grooves,wherein said conductive thin film is adapted to be displaced in responseto an applied acceleration.